Microbio Lec 4 - Microbial Flora in Health and Disease

MICROBIOLOGY LECTURE 4 – Microbial Flora in Health and Disease - Dra. Evelina N. Lagamayo Notes from Lecture USTMED ’07 Sec C – AsM Factors that determine microbial flora in and on the human body: 1. Age 2. Diet 3. Hormonal state 4. Health 5. Sanitary conditions 6. Personal hygiene

C.

Eye colonizer 1. coagulase-negative staphylococcus 2. Potential pathogens a. Hemophlius spp. b. Neisseria spp. c. Viridans streptococci

D. -

Lower Respiratory Tract larynx, trachea, bronchioles and lower airways are generally sterile 1. acute lower airway disease: a. Strep. Pneumoniae b. Staph. Aureus c. H. influenza d. Members of Enterobacteriaceae (Klebsiella spp.) 2. chronic aspiration o polymicrobial disease a. anaerobes (Peptostreptococci) b. and anaerobic gram negative bacilli c. Candida spp. demonstrated in tissue d. Dimorphic fungi (Histoplasma, Coccidioides, Blastomyces spp.)

E.

Gastrointestinal Tract 1. stomach a. lactic acid-producing bacteria b. Lactobacilli c. Streptococci d. Helicobacter pylori o affected by drugs that neutralize or reduce production of gastric acid 2. Small intestines o bacteria, fungi and parasites o Common casues of gastroenteritis  Salmonella spp  Campylobacter spp. 3. Large intestines a. Anaerobes:  avirulent bifidobacteria  eubacteria  Peptostreptococci  Bacteroides fragilis group b. Facultative anaerobes  Enterobacteriaceae  Enterococci c. Antibiotic-resistant organisms  Enterococci  Pseudomonas  Fungi  Clostridium difficile-diarrhea to pseudomembranous colitis d. Enteric pathogens:  Shigella  Enterohemorrhagic E. coli (EHEC)  Entamoeba histolytica

F.

Genitourinary System 1. Anterior urethra a. avirulent organisms:  lactobacilli  corynebeacterium  coagulase negative staphylococci b. colonizers that can lead to disease:  enterococci  Enterobacteriaceaaae  Candida c. Asymptomatic colonizers:  Neisseria gonorrhea  Chlamydia trachomatis d. Significant irregardless of the presence or absence of symptoms 2. Vagina a. Newborn girls  Lactobacilli from birth up to 6 weeks  Staphylococcus  Streptococcus  Enterobacteriaceae b. Puberty  Lactobacilli  Staph aureus  Coagulase negative staph  Streptococcus (group B)  Enterococci  Gardnerella vaginilis  Mycoplasma/Ureaplasma

Two important points to be emphasized: care should be taken to maintain the normal balance of microbes An important distinction exists between colonization with pathogenic organism and disease How does Normal Microbial flora control the proliferation of Pathogenic organisms? competition for nutrients or receptors on host cells production of bacteriocins (small-molecular-weight proteins that are bactericidal for other organisms) Stimulation of immune response Normal flora is disrupted (e.g. by broad-specturm antibiotics

Pathogenic organisms are introduced into a normally sterile environment

DISEASE IS PRODUCED Example: Oro-pharyngeal flora Streptococcus pneumoniae Staphylococcus aureus Gram-negative bacilli

Aspiration of oral secretions into the lower respiratory tract

Bronchopulmonary disease Classes of Microbes according to their propensity for causing disease: 1. Opportunistic pathogens – will not cause disease except in immunocompromised patients o example: Staphylococcus epidermidis at the site of IV catheter 2. Strict pathogens – always associated with disease o example: Mycobacterium tuberculosis, Shigella spp., Neisseria gonorrhea 3. Facultative pathogens – associated with disease; majority of organisms o Example: Staphylococcus aureus, Escherichia coli, Candida albicans Respiratory Tract and Head A. Colonizers of the upper respiratory tract: 1. Anaerobic bacteria a. Peptostreptococcus b. Fusobacterium c. Prophyromonas d. Bacteroides e. Actinomyces 2. Aerobic organisms: a. Viridans group streptococci b. Coagulase-negative staphylococci c. Nonpathogenic Neisseria d. Haemophiluss spp (not H. influenza) 3. Potentially pathogenic organisms a. Group A streptococci b. Streptococcus pneumoniae c. Staphylococcus aureus d. Neisseria meningitides e. Hemophilus influenza f. Moraxella catarrhalis g. Enterobacteriaceae B. Ear colonizer 1. Coagulase negative staphylococcus 2. Potential pathogens a. Streptococcus pneumonia b. Pseudomonas aeruginosa c. Enterobacteriaceae

o

c.

G.

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Esterobactenaceae



Anaerobes

important cause of Vaginitis 1) Mobiluncus and Gardnerella 2) Mycoplasma hominis 3) Trichomonas vaginalis 4) Candida albicans 5) Torulopsis glabrata Causes of persistent infection of GUT:  Herpes simplex virus  Papillomavirus

Skin o o o o o

coagulase negative staphylococci Staphylococcus aureus, less common Clostridium perfringens, approx 20% of healthy individuals Candida and Malassezia, moist sites Streptococci, transient only (toxic volatile fatty acids produced by propionibacteria

Nosocomial Infections Definition: hospital acquired infection transmitted to patients by hospital personnel and other patients, or may arise from the patient’s own endogenous flora 1. 2. 3. 4. 5.

Modes of acquisition of Nosocomial Infections Surgical procedures Indwelling intravenous or bladder catheters Endotracheal tubes Intravenous fluids Equipment used for respiratory support

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Incidence of Nosocomial Infections o 80%> of nosocomial infections involve: a. urinary tract b. respiratory tract c. surgical wounds

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Nosocomial Infections in Acute Care Institutions

Infection Site Urinary tract

% of All Nosocomial Infection 40%

Most common agents

Surgical wounds Pulmonary

20%

Primary bacteremia Others

5-10%

E. coli, enterococcus, Proteus, Klebsiella, Pseudomonas, aeruginosa Staph aureus, Staph epidermidis, E. coli Klebsiella, Pseudomonas, E. coli, Staph aureus Staph aureus, S. epidermidis, GNB

20-25%

Staph aureus, E. coli

10%

Opportunistic Infections Definition: Infections that occur as a result of abnormalities in host defense May occur as a complication of abnormal defense mechanisms or as a result of various iatrogenic or nosocomial factors

Infections most commonly associated with immune deficiencies Defect Predisposing Condition Infection Phagocytic Acute leukemia Staphy aureus abnormalities Cytotoxic drugs S. epidermidis Radiation therapy Pseudomonas Corticosteroid therapy aeruginosa diabetes Enterobacteriaccea Candida Aspergillus Zygomycetes Splenectomy Bacterium with strep. Pneumoniae Hemophilus influenzae Complement Genetic disorders Bacteremias and abnormalities C3 deficiency pneumonias with C5-C9 deficiency encapsulated organisms Disseminated Neisseria infections Antibody Hypogammaglobulinemia Encapsulated and deficiency Multiple myeloma extracellular bacteria Lypnocytic leukemia Enterovirus Lymphomas Giardia Nephrotic syndrome Steroids or cytotoxic drug therapy CellHodgkin’s disease, Systemic infection mediated steroid therapy, with Mycobacterium immunity Cytotoxic drug therapy and other intracellular disfunction Uremia bacteria, Candida and Maltnutrition, AIDS systemic fungi, DNA viruses, protozoa, Pneumocystis, Strongyloides

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